Biomedical subjects

Ines Jentzsch

Publications and source records attributed to Ines Jentzsch.

17 recordsLinked to original sources

PubMed2006

Event related potentials and the perception of intensity in facial expressions.

It is well known from everyday experience, that facial expressions of emotions can very much vary in intensity, e.g. ranging from mild anger to rage, or from uneasiness and mild fear to angst and panic. However, the effect of different intensities of facial expressions of emotion on event related potentials has yet not been studied. We therefore investigated 16 healthy participants with a gender decision task to male and female faces displaying angry, disgusted and fearful facial expressions varying in intensity (50%, 100%, 150%). Analysis of ERP data showed a significant increase in amplitude of the N170 by intensity, but not by type of emotion. The intensity induced negative variation was most pronounced between 200 and 600ms at electrodes P9 and P10. For this time segment, there was a clear linear relationship between intensity and degree of negative deflection. A dipole source localisation of the intensity effect using the difference waveform (150% minus 50% intensity) revealed two symmetrically positioned generators within the inferior temporo-occipital lobe. An emotion specific effect for disgust was further found at temporal electrode sites (FT7 and FT8) at around 350-400ms. Results are summarised in a two-phase model of emotion recognition, suggesting the existence of an initial monitoring process which codes saliency of incoming facial information. In a second step, the specific emotional content of faces is decoded in emotion specific recognition systems.

Adult↗

PubMed2006

Control over speeded actions: a common processing locus for micro- and macro-trade-offs?

Cognitive control processes associated with long- and short-term adjustments of human behaviour have attracted much interest recently. It is still unclear, however, whether the mechanisms underlying these adjustments share a common locus within the chain of stimulus-response processing. In order to address this issue, the present study employed a speed-accuracy instruction producing a macro-trade-off, whereas micro-trade-off was studied by means of posterror slowing in reaction time (RT). Participants performed a spatially compatible or incompatible four-stimuli-to-two-response alternative choice RT task. Reliable variations in micro-and macro-trade-off as well as effects of spatial compatibility were found in RT and error rate. Most importantly, posterror slowing was larger when instruction stressed accuracy rather than speed, an effect being independent of spatial compatibility. Because the influence of speed-accuracy instruction and posterror slowing on performance was strongest for response alternations, together present findings suggest that the mechanisms underlying micro- and macro-trade-offs have one common locus at the level of motor processing. Additional influences of macro-trade-off on premotoric processing are likely.

Adolescent↗

PubMed2006

Motor limitation in dual-task processing under ballistic movement conditions.

The standard bottleneck model of the psychological refractory period (PRP) assumes that the selection of the second response is postponed until the first response has been selected. Accordingly, dual-task interference is attributed to a single central-processing bottleneck involving decision and response selection, but not the execution of the response itself. In order to critically examine the assumption that response execution is not part of this bottleneck, we systematically manipulated the temporal demand for executing the first response in a classical PRP paradigm. Contrary to the assumption of the standard bottleneck model, this manipulation affected the reaction time for Task 2. Specifically, reaction time for Task 2 increased with execution time for Task 1. This carryover effect from Task 1 to Task 2 provides evidence for the notion that response execution can be part of the processing bottleneck.

Decision Making↗

PubMed2005

Priming emotional facial expressions as evidenced by event-related brain potentials.

As human faces are important social signals in everyday life, processing of facial affect has recently entered into the focus of neuroscientific research. In the present study, priming of faces showing the same emotional expression was measured with the help of event-related potentials (ERPs) in order to investigate the temporal characteristics of processing facial expressions. Participants classified portraits of unfamiliar persons according to their emotional expression (happy or angry). The portraits were either preceded by the face of a different person expressing the same affect (primed) or the opposite affect (unprimed). ERPs revealed both early and late priming effects, independent of stimulus valence. The early priming effect was characterized by attenuated frontal ERP amplitudes between 100 and 200 ms in response to primed targets. Its dipole sources were localised in the inferior occipitotemporal cortex, possibly related to the detection of expression-specific facial configurations, and in the insular cortex, considered to be involved in affective processes. The late priming effect, an enhancement of the late positive potential (LPP) following unprimed targets, may evidence greater relevance attributed to a change of emotional expressions. Our results (i) point to the view that a change of affect-related facial configuration can be detected very early during face perception and (ii) support previous findings on the amplitude of the late positive potential being rather related to arousal than to the specific valence of an emotional signal.

Adult↗

PubMed2005

Response conflict determines sequential effects in serial response time tasks with short response-stimulus intervals.

In serial choice reaction time (RT) tasks, performance in each trial critically depends on the sequence of preceding events. In this study, the authors specifically examined the mechanism underlying RT sequence effects at short response-stimulus intervals (RSIs), in which performance is impaired in the current trial N if events alternate rather than repeat from trial N-2 to trial N-1. Different accounts of this RT pattern in terms of perceptual noise, response-selection monitoring, and response conflict were tested in 4 experiments. Second-order RT costs were caused by the response sequence rather than the stimulus sequence. Manipulation of stimulus contrast, stimulus classification difficulty, and set-level compatibility did not modulate the response-related second-order RT effect, whereas this effect increased when spatially incompatible responses were demanded. These findings support a response conflict account of higher order sequential effects in short-RSI situations.

Adult↗

PubMed2004

Face repetition effects in direct and indirect tasks: an event-related brain potentials study.

We investigated immediate repetition effects on event-related potentials (ERPs) during direct and indirect tasks for sequentially presented face pairs. The first face (F1) was presented masked or unmasked, and at different stimulus onset asynchronies (SOAs, 67 vs. 1000 ms) preceding the second face (F2). Experiment I (indirect task) required a semantic classification of F2, with F1 identity being irrelevant. Experiment II (direct task) used the same stimulus sequence but required a physical identity matching of F1 and F2. Whereas no masked repetition effects in behaviour or ERPs were seen, such effects were clearly shown for unmasked F1 faces. For short SOAs, an early-onset ( approximately 100 ms) occipital repetition effect, an inferior temporal N250r (200-300 ms) and a central-parietal N400 modulation (300-500 ms) were seen in both tasks, whereas a parietal P600 effect (500-800 ms) was only present in the indirect task. For long SOAs, the early occipital effect disappeared, suggesting that it reflects a fast decaying iconic memory trace. Clear task differences were seen for N250r, N400, and P600 modulations: P600 was larger for the indirect task, and may be a correlate of semantic analysis required by this task. By contrast, N250r and N400 were larger for the direct task, suggesting that these components are sensitive to task relevance and/or attentional focus to F1, and thus do not reflect purely automatic facilitation in processing. This suggests an influence of strategic processing on the activation of both perceptual representations of faces and semantic representations of people.

Adolescent↗

PubMed2004

Beneficial effects of ambiguous precues: parallel motor preparation or reduced premotoric processing time?

The present study was designed to investigate the mechanisms underlying movement preprogramming in situations where informative but ambiguous precue information is used. In a response precuing task that involved flexion or extension movements with the right or left index finger, a spatially compatible precue conveyed partial information about side, about direction, no parameter information (ambiguous condition), or no information at all. Advance movement preparation was indicated by reaction-time shortening for all informative precue conditions. The analysis of stimulus- and response-locked lateralized readiness potential onsets revealed a clear and exclusive motoric origin of the ambiguous-precue benefit. Additional analyses ruled out a strategic trial by trial choice of just one of the two ambiguous alternatives and provided evidence for a parallel preparation of both response alternatives when information only about direction or ambiguous precue information is provided.

Adult↗

PubMed2004

What's special about personally familiar faces? A multimodal approach.

Dual-route models of face recognition suggest separate cognitive and affective routes. The predictions of these models were assessed in recognition tasks with unfamiliar, famous, and personally familiar faces. Whereas larger autonomic responses were only triggered for personally familiar faces, priming effects in reaction times to these faces, presumably reflecting cognitive recognition processes, were equal to those of famous faces. Activation of stored structural representations of familiar faces (face recognition units) was assessed by recording the N250r component in event-related brain potentials. Face recognition unit activation increased from unfamiliar over famous to personally familiar faces, suggesting that there are stronger representations for personally familiar than for famous faces. Because the topographies of the N250r for personally and famous faces were indistinguishable, a similar network of face recognition units can be assumed for both types of faces.

Adult↗

PubMed2003

A principled method for determining the functionality of brain responses.

A challenging issue in relating brain function to perception and cognition concerns the functional interpretation of brain responses. For example, while there is agreement that the N170 component of event-related potentials is sensitive to face processing, there is considerable debate about whether its response reflects a structural encoder for faces, a feature (e.g. eye) detector, or something else. We introduce a principled approach to determine the stimulus features driving brain responses. Our analyses on two observers resolving different face categorization tasks (gender and expressive or not) reveal that the N170 responds to the eyes within a face irrespective of task demands. This suggests a new methodology to attribute function to different components of the neural system for perceiving complex stimuli.

Brain↗

PubMed2003

Neural correlates of shape from shading.

Psychophysical studies have shown that human observers resolve shape-from-shading ambiguities by assuming that light is coming from above-left. Using event-related potentials (ERPs), we measured the processing time of the perception of an ambiguous shaded pattern. We found that the N2 component followed the change of perceived shape with stimulus orientation. We also found that the P1 component in occipital and temporal areas was correlated with the observers' idiosyncratic bias for light source position. The precocity of the correlated ERP components suggests that the light source is represented early in the visual system. Altogether, our results indicate that shape-from-shading is a mostly bottom-up mechanism.

Adult↗

PubMed2003

Matching faces for semantic information and names: an event-related brain potentials study.

In face identification, it has been controversial whether or not access to biographical information and to a person's name are mediated by qualitatively different loci. We recorded ERPs while participants saw two successive faces and performed a matching task that either required retrieval of semantic information ("same or different profession?"), or retrieval of the person's name ("same or different number of forename syllables?"). For both tasks, slow ERP activity between the first and the second face was characterized by a prominent right posterior negativity, with the asymmetry being larger for the name than the semantic matching task. ERPs to the second face showed a difference between congruent (matching) and incongruent (mismatching) trials, with more negative ERPs for incongruent trials. In the semantic matching task, these differences were significant between 450 and 550 ms, and resembled an N400, with a maximum negativity over the vertex. In the name matching task, the topography of this congruency effect was qualitatively different from that seen in semantic matching. These findings suggest that different brain substrates mediate the access to semantic and name information.

Adolescent↗

PubMed2002

Spatiotemporal source localisation reveals involvement of medial premotor areas in movement reprogramming.

Response priming tasks reveal huge reaction time (RT) costs when invalidly prepared movements have to be reprogrammed after the imperative response signal. Yet, possible brain correlates of motor reprogramming have rarely been examined. The present experiments were designed to ascertain the brain correlates associated with motor reprogramming by combining the recording of event-related brain potentials (ERPs) with a spatiotemporal source-localisation approach. In two experiments either valid or invalid advance information about direction (experiment 1) and about direction and response hand (experiment 2) was provided. RTs showed considerable motor reprogramming costs in invalid trials. In both experiments reprogramming effects were reflected in ERP difference waveforms in terms of a centroparietally distributed negative and a frontal positive deviation. Source localisation of these ERP difference waveforms indicated brain activity in medial higher-order motor regions. Present findings accord with the assumption that the human pre-supplementary motor area plays an important role in motor reprogramming.

Adult↗

PubMed2002

The effect of intentional expectancy on mental processing: a chronopsychophysiological investigation.

Expected events are processed faster than unexpected ones. Previously, we have reported evidence that passive expectancies determined by the preceding event sequence mainly affected the duration of motoric processes. Here we examined the effects of instructed, intentional expectancies in a two-choice reaction time (RT) task. As predicted, RTs were shorter for expected than unexpected events. Onset of the lateralized readiness potential as an index of selective response activation, and the latency of the P300 component of the event-related potential, reflecting the duration of perceptual processing, indicated that intentional expectancy affected the time demands for central processing but did not influence the duration of early perceptual or motoric processes. Together the present and our previous results provide evidence that different kinds of expectancy can be distinguished by their locus of action within the information processing system.

Adult↗

PubMed2002

Distinguishing neural sources of movement preparation and execution. An electrophysiological analysis.

The present study examined lateralized event-related potentials (L-ERPs) associated with movement preparation and execution. In a response precuing task that involved hand and foot movements a precue conveyed either information about side and effector, side alone, or no information. Advance movement preparation was indicated by RT shortening with increasing amount of precue information. L-ERPs revealed during the preparatory interval an initial parietal activity when movement side was precued. Later in the preparatory interval L-ERPs revealed a polarity inversion for foot versus hand movements when effector and side were specified in advance. This polarity inversion showed up also in execution-related L-ERP waveforms. Comparison of preparation- versus execution-related brain signals yielded topographic differences and dissimilar dipole sources for hand-related L-ERP activity. We take present findings to indicate that brain generators within the parietal lobe and anterior MI are hierarchically related to precue-induced motor preparation, whilst posterior MI is associated with motor execution functions.

Adult↗

PubMed2002

Advance movement preparation of eye, foot, and hand: a comparative study using movement-related brain potentials.

The present study was designed to test the inter-relationship between generalized motor programs (GMPs) and movement preparation by asking participants to perform movements with eye, foot, or hand. In two independent experiments a response precuing task was employed that combined the recording of movement-related brain potentials (MRPs) with dipole source analysis. Behavioral results indicated the utilization of advance information about movement direction and effector. When eye and hand movements were involved (experiment1) partial advance information about response side but not effector induced parallel motor programming of eye and hand at an abstract but not effector-specific level. In contrast, when partial precues specified side of a forthcoming hand or foot movement (experiment 2) foot and hand were prepared in parallel both at abstract and at effector-specific levels of motor programming. Consistent with the GMP view, these results indicate that effector-specific preparation is possible even when the effector is not yet known as long as a common motor program controls the demanded movements. However, because parallel specification of divergent movement pattern (eye, hand) at an abstract level was not predicted by the GMP, we propose a model of advance movement preparation that takes into account neurofunctional considerations.

Adult↗

PubMed2002

Event-related brain potential evidence for a response of inferior temporal cortex to familiar face repetitions.

We investigated immediate repetition effects in the recognition of famous faces by recording event-related brain potentials (ERPs) and reaction times (RTs). Participants recognized celebrities' faces that were preceded by either the same picture, a different picture of the same celebrity, or a different famous face. Face repetition caused two distinct ERP modulations. Repetitions elicited a strong modulation of an N250 component ( approximately 200-300 ms) over inferior temporal regions. The N250 modulation showed a degree of image specificity in that it was still significant for repetitions across different pictures, though reduced in amplitude. ERPs to repeated faces were also more positive than those to unprimed faces at parietal sites from 400 to 600 ms, but these later effects were largely independent of whether the same or a different image of the celebrity had served as prime. Finally, no influence of repetition was observed for the N170 component. Dipole source modelling suggested that the N250 repetition effect (N250r) may originate from the fusiform gyrus. In contrast, source localisation of the N170 implicated a significantly more posterior location, corresponding to a lateral occipitotemporal source outside the fusiform gyrus.

Adolescent↗

PubMed2002

Functional localization and mechanisms of sequential effects in serial reaction time tasks.

Reaction times (RTs) to randomly ordered stimuli are influenced in various ways by the sequence of preceding events. Depending on the response-stimulus interval and stimulus-response compatibility, cost-only or cost-benefit patterns can be observed. In order to localize these effects within the information-processing system, different sequential patterns were induced in overt performance. RTs and amplitude developments of the lateralized readiness potential (LRP) across several trials indicated the accumulation of residual traces as a possible mechanism underlying sequential effects. Analysis of LRP onsets indicated two possible loci of action of such traces. Whereas in motoric stages trace accumulation appeared to produce processing advantages only for continued event repetitions, without corresponding costs for discontinuations, cost-benefit patterns were consistently observed in premotoric stages.

Adolescent↗